Lubricated plastic impregnated wire rope

ABSTRACT

A wire rope, and method of making same, is provided wherein the wire rope strands are coated with a heavy viscous lubricant prior to winding the strands into rope, and the lubricated rope is impregnated with a thermoplastic material to entrap the lubricant in the strands and core. The outer strands are held in spaced relationship during the plastic impregnating step, and the plastic material does not extend beyond the outer periphery of the wire rope.

United States Patent [1 1 Riggs [111 3,824,777 July 23, 1974 LUBRICATEDPLASTIC IMPREGNATED WIRE ROPE Peter Philip Riggs, Essex, England AmstedIndustries Incorporated, Chicago, 111.

Oct. 5, 1973 Inventor:

Assignee:

Filed:

Appl. No.:

US. Cl. 57/149, 57/162 Int. Cl D07b 1/16, D07b 7/12, D07b 7/14 Field ofSearch 57/139, 144, 145, 149,

References Cited UNITED STATES PATENTS 1/1936 Hodson 57/149 X l/1936Hodsoni.

Whyte....

Dietz 57/149 Lang 57/149 X Dietz 57/149 Riggs 57 149 Smallinger 57/153 xPrimary Examiner-Donald E. Watkins [5 7 ABSTRACT A wire rope, and methodof making same, is provided wherein the wire rope strands are coatedwith a heavy viscous lubricant prior to winding the strands into rope,and the lubricated rope is impregnated with a thermoplastic material toentrap the lubricant in the strands and core. The outer strands are heldin spaced relationship during the plastic impregnating step, and theplastic material does not extend beyond the outer periphery of the wirerope.

7 Claims, 3 Drawing Figures LUBRICATED PLASTIC IMPREGNATED WIRE ROPEThis invention relates to wire rope and particularly to the plasticimpregnation of a lubricated wire rope.

There are many known methods of impregnating wire rope with varioustypes of thermoplastic material for the purpose of improving fatiguelife, reducing wire contact stresses, and inhibiting corrosion. It hasbeen found, however, that prior art impregnated wire ropes have notalways been entirely satisfactory. For example, it has been consideredvirtually impossible to plastic-impregnate a lubricated wire ropebecause of the gas created by the lubricant at the elevated temperaturesrequired for plastic impregnation. For this reason, it has been standardprocedure to clean and degrease all wire rope which was to be plasticimpregnated. Furthermore, during the course of fabrication some of therope strands are in contact while others have excess separation, therebymaking uniform impregnation difficult to accomplish.

Two known methods exist for overcoming the latter difficulty. Controlledstrand separation in plastic impregnated wire ropes has been achieved bythe inclusion of oversized control wires in the strands, or by the useof the conventional parallel lay construction wherein the rope strandsand core strands are integrated and closed simultaneously to the samelay length. Even the parallel lay construction, however, is limited to asteel wire rope core and only approximates even strand separation. Bothof the foregoing methods have their limitations in that the first methodrequires special fabrication while the second method obviously limitsthe choice of constructions available for plastic impregnation.

It is a primary object of the present invention to produce a standardstock, heavily lubricated wire rope process to be described hereinaftermay be applied to The lubricated wire rope is then preheated to atemwhich is impregnated with a load bearing thermoplastic such that theviscous lubricant is entrapped in the strands and core, the rope havinga consistent wall thickness of plastic between the external wire ropestrands.

Another object is to provide a lubricated plastic impregnated wire ropehaving a smooth, continuous outer periphery with increased bearing areabut without increased rope diameter.

These and other objects and advantages will be apparent from thefollowing description and accompanying drawings wherein:

FIG. 1 is a cross-sectional view of a typical wire rope formed inaccordance with the teaching of the present invention;

FIG. 2 is a longitudinal sectional view through the strand gapcontroller and extruder head utilized in carrying out the method andforming the wire rope of the invention; and

FIG. 3 is an end elevational view of the strand gap controller.

The present invention utilizes a conventional wire rope 10 whereinindividual wires 12 are wound into strands l4, and a plurality ofstrands are formed about a core 16 which is also preferably formed of aplurality of strands 18. It should be understood that the strands of thecore 16 may be formed of a fiber material such as hemp instead ofmetallic wires as indicated in the drawings. The particular rope shownin FIG. 1 is given by way of example because the plastic impregnatingperature in the range of to 275F., although best results are attained ifthe preheat temperature is in the range of to F. This preheating step isone of the two critical steps in the method of fabrication of thisinvention because at the temperatures involved, the lubricant does notform a gas during the later step of plastic impregnation. The othercritical step in the novel process is the balanced separation of theouter strands of the wire rope at the time of plastic impregnation. Thisbalanced separation of the strands is achieved by means of a strand gapcontroller mounted on the rope input side of a plastic extruder as shownin FIGS. 2 and 3. The strand gap controller serves to balance andequalize the strand lay at the exact moment of plastic impregnation sothat the internal and external interstices between the strands arefilled with equal amounts of thermoplastic, this being accomplished atlower temperatures than heretofore thought possible.

Referring to FIGS. 2 and 3, it is seen that the strand gap controller,indicated generally at 20 comprises a stationary outer casing 22 inwhich is rotatably mounted, by means of suitable bearings 24, acylindrical head 26. Secured internally of and rotatable with head 26 isa strand profile insert 28. Passing through the center of insert 28 isan opening 30 formed to the contour of the outer strands of theparticular rope being processed. As anon-rotating wire rope is fedaxially through opening 30 with the outer rope strands fitting intoindividual strand slots 32, the strand profile insert rotates, as therope advances, so as always to positively hold the strands equallyspaced from each other.

The wire rope passes from the strand gap controller directly intoextruder head 34, suitably mounted coaxially with the strand gapcontroller. The extruder may be of any conventional design and is shownas comprising a crosshead 36 having an opening 38 arranged to receive amandrel holder 40 which carries a mandrel 42. Encircling the mandrel endof holder 40 and forming therewith a passage 44 is a die ring 46 held inposition by a die retainer 48 and a face plate 50.

Secured to the output end of the die retainer 48 is a die holder 52 intowhich is threaded a die 54.

As the preheated wire rope emerges from the strand gap controller andpasses through the extruder head, a flexible thermoplastic 55 (FIG. 1)is extruded, under a pressure in the range of about 2,000 to 4,000 PSIinto the interstices of the rope, completely filling them down to theouter strands of the core. The thermoplastic can be any of those capableof being extruded such as polypropylene, polyurethane, polyethylene,nylon or tetrafluor oethylene. The opening 56 in the die 54 controls thecoating thickness and in the present embodiment is just large enough topermit the wire rope to pass through, thereby limiting the diameter ofthe plastic to the nominal diameter of the wire. rope, as seen in FIG.1.

impregnation of a lubricated wire rope with plastic as described aboveprevents entrance of foreign abrasive particles into the rope whilesealing lubricant inside the rope, thereby increasing the rope servicelife. Another advantage is a reduction in wire notching effect andinternal friction because the loads placed on the rope are sharedsubstantially equally by the spaced internal wires. Furthermore, alubricated wire rope, impregnated with plastic while holding the outerstrands spaced from each other, will have extremely good resistance tofatigue and an increased ultimate breaking strength because of areduction in internal wire contact, all while maintaining flexibility.

What is claimed is:

1. A method of making a wire rope comprising the steps of: windingindividual wires into strands; forming a plurality of strands about alubricated core into a multi-strand rope while simultaneously coatingthe strands with a heavy viscous lubricant; preheating the rope to atemperature in the range of about 100 to 275F.;

holding the outer strands of the wire rope spaced from each other and,while said strands are spaced, impregnating the rope with a plasticcomposition so as to entrap the lubricant in the core and the strands,the outer diameter of the plastic conforming substantially to the outerdiameter of the rope.

2. A method according to claim 1, wherein the spacing step includesfeeding the wire rope through a strand gap controller having an openingwith its peripheral configuration conforming to the outer periphery of awire rope with equally spaced outer strands.

. 3. A method of making a lubricated plastic'impregnated wire rope,comprising the steps ofzwinding iridividual lubricated wires intostrands; forming a plurality of strands about a core into a multi-strandrope while simultaneously coating the core and the strands with a heavyviscous lubricant; heating the rope to a temperature in the range ofabout F. to F.; feeding the heated, lubricated rope through a strand gapcontroller to hold the outer rope strands equally spaced from each otherand, while the outer rope strands are so spaced, extruding athermoplastic composition under pressure into the rope to surround therope strands to a predetermined depth and entrap the lubricant in therope, the outer diameter of the plastic conforming substantially to theouter diameter of the rope.

4. A method according to claim 3 wherein the extrusion pressure is inthe range of about 2,000 to 5,000 pounds per square inch.

5. A wire rope comprising: a lubricated core, a plurality of lubricatedwire strands laid around said core, and a thermoplastic material fillingthe spaces between said strands to retain the lubricant in the core andin the strands, said thermoplastic material extending outwardly only tothe outer periphery of the wire rope.

6. A wire rope according to claim 5 wherein said plurality of wirestrands are equally spaced apart in circumferential direction.

7. A wire rope according to claim 6 wherein the thermoplastic materialextends inwardly to the wire rope core.

1. A method of making a wire rope comprising the steps of: windingindividual wires into strands; forming a plurality of strands about alubricated core into a multi-strand rope while simultaneously coatingthe strands with a heavy viscous lubricant; preheating the rope to atemperature in the range of about 100* to 275*F.; holding the outerstrands of the wire rope spaced from each other and, while said strandsare spaced, impregnating the rope with a plastic composition so as toentrap the lubricant in the core and the strands, the outer diameter ofthe plastic conforming substantially to the outer diameter of the rope.2. A method according to claim 1, wherein the spacing step includesfeeding the wire rope through a strand gap controller having an openingwith its peripheral configuration conforming to the outer periphery of awire rope with equally spaced outer strands.
 3. A method of making alubricated plastic impregnated wire rope, comprising the steps of:winding individual lubricated wires into strands; forming a plurality ofstrands about a core into a multi-strand rope while simultaneouslycoating the core and the strands with a heavy viscous lubricant; heatingthe rope to a temperature in the range of about 120*F. to 160*F.;feeding the heated, lubricated rope through a strand gap controller tohold the outer rope strands equally spaced from each other and, whilethe outer rope strands are so spaced, extruding a thermoplasticcomposition under pressure into the rope to surround the rope strands toa predetermined depth and entrap the lubricant in the rope, the outerdiameter of the plastic conforming substantially to the outer diameterof the rope.
 4. A method according to claim 3 wherein the extrusionpressure is in the range of about 2,000 to 5,000 pounds per square inch.5. A wire rope comprising: a lubricated core, a plurality of lubricatedwire strands laid around said core, and a thermoplastic material fillingthe spaces between said strands to retain the lubricant in the core andin the strands, said thermoplastic material extending outwardly only tothe outer periphery of the wire rope.
 6. A wire rope according to claim5 wherein said plurality of wire strands are equally spaced apart incircumferential direction.
 7. A wire rope according to claim 6 whereinthe thermoplastic material extends inwardly to the wire rope core.